This invention relates to an improved sector assembly for a rotary disc vacuum filter.
Disc filters are well known in the filtration art. A typical disc filter includes a series of generally fan-shaped filter sector assemblies secured at close intervals around a rotatable supportive shaft. Each sector assembly includes a fan-shaped sector body and a bell-shaped conduit or member connecting the body to the shaft. Each sector body is covered individually with a filter medium to provide filtering on opposing faces of the body. The faces of the sector body are typically provided with grooves which are interconnected by the bell member to a conduit formed in the supporting shaft through which a vacuum is drawn to draw liquid filtered through the filter medium.
Various filter sector assemblies are known in the art, for example wooden sector assemblies, plastic sector assemblies and combinations thereof. Of these, plastic sector assemblies are particularly desirable due to their resistance to corrosive materials and to their comparative lightness in weight which eases handling. However, these plastic sector assemblies present a challenge in the form of providing sufficient structural strength to the assembly to prevent buckling of the assembly, for example along the connection of the sector body to the bell-shaped conduit.
U.S. Pat. Nos. 3,917,534 and 3,485,376 teach plastic sector assemblies. In U.S. Pat. No. 3,917,534, structural strength is provided to the assembly by forming a plastic sector body with a hollow interior which is filled with a second plastic material. A further technique taught by this patent for providing strength is molding the plastic body around metal rods which extend internally through the body of the sector and are employed to secure the body to a bell member.
In U.S. Pat. No. 3,485,376, structural strength is provided by forming a sector body with a plurality of intermediate sections. These intermediate sections are then secured together to form the body with structural pieces which circumscribe the body. The structural pieces extending along the radial sides of the body impede replacement of a filter medium overlying the body by being positioned outside the filter medium.